Structure and Assembly Mechanism for Heteromeric Kainate Receptors

Laboratory of Cellular and Molecular Neurophysiology, Porter Neuroscience Research Center, NICHD, NIH, DHHS, Bethesda, MD 20892, USA.
Neuron (Impact Factor: 15.05). 07/2011; 71(2):319-31. DOI: 10.1016/j.neuron.2011.05.038
Source: PubMed


Native glutamate receptor ion channels are tetrameric assemblies containing two or more different subunits. NMDA receptors are obligate heteromers formed by coassembly of two or three divergent gene families. While some AMPA and kainate receptors can form functional homomeric ion channels, the KA1 and KA2 subunits are obligate heteromers which function only in combination with GluR5-7. The mechanisms controlling glutamate receptor assembly involve an initial step in which the amino terminal domains (ATD) assemble as dimers. Here, we establish by sedimentation velocity that the ATDs of GluR6 and KA2 coassemble as a heterodimer of K(d) 11 nM, 32,000-fold lower than the K(d) for homodimer formation by KA2; we solve crystal structures for the GluR6/KA2 ATD heterodimer and heterotetramer assemblies. Using these structures as a guide, we perform a mutant cycle analysis to probe the energetics of assembly and show that high-affinity ATD interactions are required for biosynthesis of functional heteromeric receptors.

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    • "In eukaryotic pentameric LGICs (pLGICs) such as the a7 nAChR (Castillo et al., 2009), the r1 GABA C R (Wong et al., 2014) and the a1 or a1b GlyRs (Kuhse et al., 1993; Griffon et al., 1999) intersubunit interactions of the N-terminal domains were shown to be critical for assembly. Also, in heteromeric kainate receptors, high-affinity interaction domains of the KA2 and GluR6 subunits control subunit assembly (Kumar et al., 2011). The resolution of the zebrafish P2X4 receptor X-ray structure has shown the extracellular contact interfaces of adjacent subunits (Kawate et al., 2009), which has together with mutagenesis studies (Hausmann et al., 2015) shed light on the intersubunit interaction domains that control subunit assembly of P2X receptors. "
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    • "The crystal structure of the AMPA GluA2 receptor (PDB ID: 3KG2) (Sobolevsky et al., 2009) was selected as the main template. Additional templates were used for the N-terminal domain (crystal structure of the GluK2/GluK5 NTD tetramer assembly, PDB ID: 3QLV) (Kumar et al., 2011) and the ligand-binding domain (crystal structure of GluK1 ligand-binding domain (S1S2) in complex with an antagonist , PDB ID: 4DLD) (Venskutonyt_ e et al., 2012). Homology modeling was carried out with Modeler v. 9.11 (Eswar et al., 2006). "
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    • "This notion is echoed by the finding of reduced surface expression of GluA2 lacking its amino terminal domain (ATD) for dimerization (Kumar et al., 2011). Dimerization of dimers is another common theme for Kv channels (Tu and Deutsch, 1999) and glutamate receptors (Kumar et al., 2011). "
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